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California Statewide Groundwater Elevation Monitoring

In November 2009, Senate Bill SBX7-6 mandated that all groundwater elevations in all basins and subbasins in California be regularly and systematically monitored with the goal of demonstrating seasonal long-term trends in groundwater elevations. In accordance with the mandate, the California Department of Water Resources (DWR) developed the California Statewide Groundwater Elevation Monitoring (CASGEM) program. DWR is facilitating the statewide program which began with the opportunity for local entities to apply to DWR to assume the function of regularly and systematically collecting and reporting groundwater level data for the above purpose. These entities are referred to as Monitoring Entities. The Solano County Water Agency is the Monitoring Entity under CASGEM for Solano County.

Well designed for inclusion in the CASGEM program are for the purposes of measuring groundwater levels on a semi-annual or more frequent basis that are representative in the state’s groundwater basins and subbasins. Locally, we are measuring the Solano Subbasin which is considered a medium priority subbasin under DWR’s Bulletin 118. SCWA is also providing data on the Suisun-Fairfield subbasin on a voluntary basis.

There are locations in the county where SCWA does not have complete groundwater data, because wells in these locations are private wells and data collection is not required under CASGEM. Under the Sustainable Groundwater Management Act, collection of private well data will likely occur in portions of the county. Analysis of current groundwater conditions, based off of data SCWA has collected and from other local agency’s, such as Solano Irrigation District, the City of Vacaville, Rural North Vacaville Water District, and many others, indicates that the Solano Subbasin has generally stable groundwater levels. Recent efforts to correlate existing wells that have water level data to a specific aquifer unit, a review of hydrographs for shallow and intermediate depth wells indicate generally stable groundwater levels. Since the the late 1950’s, and since the Solano Project (Lake Berryessa) has provided a substantial amount of water for agricultural purposes, and where previously a heavy reliance on groundwater resulted in groundwater level declines in some places, those declines have mostly leveled off or recovered to early historic levels.

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